Year	PPP $ per kg of oil equivalent
1990	5.744177145108205
1991	5.903261867396624
1992	6.22337283100578
1993	5.952346912862227
1994	6.206907858248583
1995	6.159399300166487
1996	6.518500763112966
1997	6.7550190500440515
1998	7.056753192104467
1999	7.147052891925294
2000	7.695927562032087
2001	7.5665613155640035
2002	7.653595308636632
2003	7.51535611569673
2004	7.9061354249166
2005	7.8547335380932335
2006	8.536654241031794
2007	9.008356277686019
2008	9.633327334810676
2009	9.459057541657332
2010	10.343321537461055
2011	10.837163902181008
2012	10.971322804967565
2013	11.193965992414546
2014	11.992987281398182
2015	12.326101356320256